In general terms, this invention relates to pen style injectors, more particularly, this invention relates to a pen style injector having an automated feature for combining at least two substances such as reconstituting a lyophilized medicament prior to performing an injection.
A wide variety of syringes and injectors are commercially available. One type of injector that is popular is sometimes referred to a pen style injector because the injector body resembles a writing pen. Pen injectors have proven convenient in a wide variety of applications.
One difficulty associated with using conventional pen style injectors occurs when the drug or medicament that is to be administered is provided in a lyophilized form. Lyophilized substances typically are supplied in a freeze-dried form that needs to be mixed with a liquid to reconstitute the substance into a form that is suitable for making an injection. Other substances that require reconstitution are provided in powder form. Under some circumstances, the reconstitution procedure must be performed carefully and at a controlled rate to ensure appropriate reconstitution.
The problem with conventional injectors is that they are dependent upon manual activation to complete a reconstitution procedure. The individual typically has to rotate different portions of the injector relative to each other using a screw-type action to move components within the injector to complete a reconstitution process. Examples of such devices are shown in U.S. Pat. No. 4,874,381 issued to Vetter, and U.S. Pat. No. 4,968,299 issued to Ahlstrand et al., the teachings of each being incorporated by reference into this specification. In other designs relative axial movements are used to accomplish the reconstitution. Such procedures can prove difficult for some individuals and potentially introduce ergonomic concerns.
Moreover, manual reconstitution procedures typically cannot be performed at a consistently controlled rate. Certain lyophilized substances require reconstitution at a controlled rate to ensure that the lyophilized substance is appropriately reconstituted. For example, some medicaments will foam up if the reconstituting liquid is introduced too quickly. A foamed medicament is typically not suitable for injection and, therefore, manual reconstitution procedures present the possibility for requiring an extended waiting period before administering a particular dosage. Additionally, there may be uncertainty regarding whether the substance is ready for making an injection.
Another potential problem associated with manually activated pen style injectors is that the reconstitution process may not be performed completely. Without appropriate controls, under some circumstances, its possible for an individual to fail to completely reconstitute the lyophilized or powder-form medicament. Under such circumstances, the incompletely reconstituted medicament may have a reduced or ineffective efficacy.
This invention provides an improved pen style injector that avoids the shortcomings and drawbacks discussed above. An injector designed according to this invention includes an automated combining or reconstitution feature that is not dependent upon manual operation and consistently provides a controlled combination or reconstitution rate.
In general terms, this invention is an injector device that is useful for combining multiple substances prior to performing an injection with the same device. An injector designed according to this invention includes a body and a substance retaining portion. The preferred retaining portion has at least a first chamber and a second chamber with a communication passage between the two chambers. The first chamber contains a first substance such as a lyophilized medicament while the second chamber contains a second substance such as liquid for reconstituting the lyophilized medicament. The injector device includes an automated mover that automatically moves the second substance from the second chamber through the communication passage and into the first chamber to automatically combine the substance prior to injecting the substances into a patient.
The currently preferred embodiment includes a mechanical spring that is preloaded within the body. When the mechanical spring is released the physical force provided by the spring automatically moves appropriate components within the injector to complete the combination or reconstitution process in an automated fashion.
The preferred embodiment not only automatically combines at least two substances but also automatically primes the injector for an injection. The automated mover preferably ensures that the substances are combined automatically and that any air bubbles within the combined substances are expelled from the injector.
Another feature of the preferred embodiment is a safety locking mechanism that prevents premature activation of the injector prior to appropriately mixing the substances within the retainer portion. The components of the injector preferably are designed such that a trigger or button for performing an injection cannot be moved go until after the components that effect the desired mixing of the substances have moved into position indicating that the mixing is complete. Cooperating grooves and ribs on the components of the injector preferably prevent the injection trigger from being moved into a position where an injection becomes possible until after the automated mixing has been completed.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.